Various plastic lenses such as prism lenses are produced by a method in which a resin material is poured into a die, a transparent plastic substrate is placed on the resin material, and the resin material is cured by being heated or by being irradiated with an active energy ray. Therefore, the resin material used to produce plastic lenses needs to have a low viscosity without using a solvent so that the resin material completely fills every cavity of a die and thus has the same shape as that of the die. The resin material also needs to form into a cured product having good physical properties, e.g., optical properties such as a refractive index and transparency, workability such as good releasability from a die, prevention of curling after curing, high flexibility, prevention of cracking and chipping caused by external forces, and good adhesiveness to a transparent plastic substrate.
Among resin materials used for plastic lenses, a compound having a fluorene skeleton has received attention because such a Compound forms into a cured product having a high refractive index. However, the cured product is brittle and has low toughness. When the compound having a fluorene skeleton is used, it is difficult to achieve both toughness and a high refractive index of the cured product. For example, a technology has been known in which the adhesiveness of a cured film to a substrate film, the releasability from a die, solvent resistance, and curling resistance are achieved by using, as a resin composition for plastic lenses, a resin composition including a diacrylate compound having a fluorene skeleton and ortho-phenylphenoxyethyl acrylate (refer to PTL 1). However, since the monoacrylate compound having a fluorene skeleton forms into a brittle cured product as described above, a cured product composed of the resin composition disclosed in PTL 1 has low toughness, and a film composed of the cured product is cracked or chipped when cutting. Furthermore, a compound having a fluorene skeleton generally has a high viscosity. If the resin composition contains such a compound having a fluorene skeleton, only compounds having a relatively low viscosity can be used as other components of the resin composition.